As stated above, the indisputable sign of Tammuz, the mystic Tau of the Babylonians and Egyptians, was brought into the Church chiefly because of Constantine, and has since been adored with all the homage due only to the Most Hight. The Protestants have for many years refrained from undue adoration of, or homage to, the cross, especially in England at the time of the Puritans in the 16th and 17th centuries. But lately this un-Scriptural symbol has been increasingly accepted in Protestantism. We have previously discussed "the weeping for Tammuz," and the similarity between the Easter resurrection and the return or rising of Tammuz. Tammuz was the young incarnate Sun, the Sun-divinity incarnate. This same Sun-deity, known amongst the Babylonians as Tammuz, was identified with the Greek Adonis and with the Phoenician Adoni, all of them Sun-deities, being slain in winter, then being "wept for," and their return being celebrated bu a festivity in spring, while some had it in summer–according to the myths of pagan idolarty.
The evidence for its pagan origin is so convincing that The Catholic Encyclopedia admits that "the sign of the cross, represented in its simplest form by a crossing of two lines at right angles, greatly antedates, in both East and the West, the introduction of Christianity. It goes back to a very remote period of human civilization." It then continues and refers to the Tau cross of the pagan Egyptians, "In later times the Egyptian Christians (Copts), attracted by its form, and perhaps by its symbolism, adopted it as the emblem of the cross."
Further proof of its pagan originis the recorded evidence of the Vestal Virgins of pagan Rome having the cross hanging on a necklace, and the Egyptians doing it too, as early as the 15th century B.C.E. The Buddhists, and numerous other sects of India, also used the sign of the cross as a mark on their followers' heads. "The cross thus widely worshipped, or regarded as a 'sacred emblem,' was the unequivocal symbol of Bacchus, the Babylonian Messiah, for he was represented with a head-band convered with crosses."
After Constantine had the "vision of the cross," he ahd his army promoted another variety of the cross, the Chi-Rho or Labarum. This has subsequently been explained as representing the first letters of the name Christos, But again, this had a pagan origin. They were found as inscriptions on rock, dating from the year ca. 2500 B.C.E., being interpreted as "a combination of two Sun-symbols, known as the Ax- or Hammer-symbol of the Sun- or Sky-deity, and the + or X as the ancient symbol of the Sun, both of these signs having a sensual or fertility meaning as well. Another proof of its pagan origin is found on a coin of Ptolemeus III from the year 247-222 B.C.E.
A well-known encyclopedia describes the Labarum (Chi-Rho) as, "The labarum was also an emblem of the Chaldean (Babylonian) sky-god and in Christianity it was adopted…" Emperor Constantine adopted this Labarum as the imperial ensign and thereby succeeded in "uniting both divisions of his troops, pagans and Christians, in a common worship…
According to Suicer the word (labarum) came into use in the reign of Hadrian, and was probably adopted from one of the nations conquered by the Romans." It must be remembered that Hadrian reigned in the years 76-138 C.E., that he was a pagan emperor, worshipped the Sun-deity Serapis when he visited Alexandria, and was vehemently anti-Judaistic, beign responsible for the final near-destruction of Jerusalem in the year 130 C.E.
Another dictionary relates the following about the Chi-Rho, "However, the symbol was in the use long before Christianity, and X (Chi) probably stood for Great Fire or Sun, and P (Rho) probably stood for Pater or Patah (Father). The word labarum (la-baar-um) yields everlasting Father Sun."
http://messianicfellowship.50webs.com/cross.html
Chi Rho Symbol seen on
The Sarcophagus of Domatilla,
Museo Pio Christiano, The Vatican